Studies on Cataractin, a yellow lipid polymer which accumulates in human senile cataracts are being conducted and supported by this grant. Cataractin is isolated by a procedure developed in this laboratory, consisting of more than fifty extraction and purification steps. Its precise chemical structure is being elucidated by use of thin layer chromatography, gas liquid chromatography, infrared spectrometry and mass spectrometry. Cataractin is bound to large protein molecules (apoprotein) forming a water soluble proteolipid. Studies on the metabolic pathways resulting in Cataractin storage and its binding to apoprotein may clarify the molecular abnormalities in human senile cataracts. Causes of other forms of human cataracts are studied in animal experiments such as the cataracts associated with uveitis or ocular inflammations. It was found that the aqueous humor of animals with uveitis contain certain phospholipids (lysophosphatidyl choline) which can induce cataracts when tested on the rabbit lens in culture. The specific site of damage to the lens by lysophosphatidyl choline is investigated in a cooperative project involving biochemical and electron microscopic techniques.